Currently, various methods are known for drilling holes in the aforementioned components, particularly the use of certain laser devices. For example, the use of diode pumped solid state lasers (DPSSL), arranged with Q switch means for the resonator, has been proposed. Such lasers generate a plurality of pulses whose very short period is generally much less than 1 μs, for example 15 nanoseconds.
A laser device of the aforementioned type has already been made by various companies. The user of such a diode pumped crystal laser has numerous advantages relative to a flash lamp pumped crystal laser, for example an Nd:YAG laser. Indeed, the use of such a flash lamp generates variations from one pulse to another, particularly a fluctuation in the intensity of the pulses supplied and a variation in the leading edge length of the pulses. Moreover, the resonator's stability is not very good, in particular because the active element is heated by the flash lamp which has a relatively broad transmission spectrum. The laser thus does not have optimum yield since a part of the energy is not used for generating the laser beam. This also means that the active medium is subjected to thermal stresses which decrease the pulse transmission stability and quality. The major drawbacks of this are that the precision of the holes to be machined is limited and it is not possible to achieve good reproducibility from one hole to the next. Thus, the geometry of the holes made by flash lamp pumped lasers has poor machining tolerances and does not allow the flow of a fluid through such holes to be precisely determined.
However, machining holes using a laser device fitted with a Q switch providing trains of pulses of very short length, within the nanosecond range, raises problems of efficiency for machining holes. Indeed, machining holes, particularly of a certain depth, requires a large number of such successive pulses, which limits the machining speed for such holes and thus the industrial yield of such machining. Moreover, this type of laser device is relatively inflexible since it does not enable the profile of the pulses generated by the resonator to be varied to obtain pulses with an intensity profile suited to machining each different type of hole. The machined hole geometry is thus difficult to vary due to the lack of adjustment flexibility of the parameters defining the very short pulses generated by the resonator. Further, holes of a relatively large diameter cannot be machined with pulses in the nanosecond range without using a machining method requiring drilling several holes along a circular outline. Finally, the Q switch frequency is limited because of the formation of a plasma during a short period, the plasma absorbing the luminous energy from a following pulse if it is still present above the hole machining area.
It is an object of the present invention to provide a laser device for drilling holes in fluid injection device components, particularly for fuel, which has good operating stability, a high level of hole machining precision and which allows said holes to be machined at a relatively high speed to obtain a high industrial yield.
It is another object of the invention to provide a device of this type that limits the necessary investment costs while preserving the efficiency thereof.